
import {
	Blob,
	btoa,
	createImageBitmap,
	CSSStyleDeclaration,
	performance,
	document,
	DOMParser,
	EventTarget,
	fetch,
	Headers,
	HTMLCanvasElement,
	Image,
	HTMLImageElement,
	ImageBitmap,
	location,
	navigator,
	Request,
	requestAnimationFrame,
	cancelAnimationFrame,
	Response,
	URL,
	window,
	self,
	WebAssembly,
	Worker,
	XMLHttpRequest,
	ImageData,
	TextDecoder,
	core
	} from 'dhtml-weixin';
import { tslFn } from '../shadernode/ShaderNode.js';

export const getDistanceAttenuation = tslFn( ( inputs ) => {

	const { lightDistance, cutoffDistance, decayExponent } = inputs;

	// based upon Frostbite 3 Moving to Physically-based Rendering
	// page 32, equation 26: E[window1]
	// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
	const distanceFalloff = lightDistance.pow( decayExponent ).max( 0.01 ).reciprocal();

	return cutoffDistance.greaterThan( 0 ).cond(
		distanceFalloff.mul( lightDistance.div( cutoffDistance ).pow4().oneMinus().clamp().pow2() ),
		distanceFalloff
	);

} ); // validated
